<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>

    </script>
</body>
<!-- <script src="hello.js"></script> -->
<!-- <script>
    //变量
    let num1=100;
    let str1,str2='hello';
    console.log(num1);
    num1=11110;
    console.log(num1);
</script> -->
<script>
    let flag = true;//或flase  得小写才是bool型
    console.log(flag);//true
    console.log(typeof(flag));//数据类型
    let num1=123,num2=0x23;
    console.log(num1);
    console.log(num2);
    console.log(typeof(num1));
    console.log(typeof(num2));

    console.log('--------------');
    let str1 = '',str2 = 'hello', str3 = 'javascript';
    console.log(str1);
    console.log(str2);
    console.log(str3);
    console.log(typeof(st1));
    console.log(typeof(st2));
    console.log(typeof(st3));
    //子曰：'学而时习之，不亦说乎'
    //在双引号中使用双引号，或在单引号中使用单引号，需使用\进行转义
    let str = "子曰（\“老子\”）:'学而时习之，不亦说乎'";
    console.log(str);
    console.log('------');
    let n1 = null,n2;
    console.log(n1);
    console.log(n2);//因为未定义所以运行出的结果为 undefined

</script>
</html>